1991 Mustang LX - Cammer Commuter

A Blown Four-Valve Revived Jason Kelly's Fox As A Daily Driver

We all want reliable transportation to take to work and back, right? Nothing temperamental, just something that will do the commute thing without leaving us stranded at the side of the road watching all that rush-hour traffic creep slowly past. Something that can idle as long as need be without loading up-or melting down. In that regard, Jason Kelly is no different from the rest of us. He wants dependability, he wants comfort, and he wants air conditioning to keep him chillin' in the heat of a Kansas summer.

But, alas, he also wants something north of 600 hp. He wants it to come from a Four-Valve modular in his '91 hatchback, and, being the humble, shy, and retiring type, he wants the LX to remain understated-close to stock, in fact-in outward appearance. These interesting criteria formed the basis for Jason's "Project Street Sleeper," and the results are equally interesting.

Jason's aspirations weren't always this high. He bought the Vermilion Red 5.0 in 1999, enjoyed it with simple bolt-ons for a couple years, then added a ProCharger D-1SC, in which form he drove the car daily for another two years at a lofty 16 psi of boost. Then, as Jason describes, "One day I had a tensioner go bad and lost the 12-rib pulley, locking up the motor and breaking the crank in the 5.0." Ouch.

Ironically, at about the same time, a good friend had written off his 8,000-mile '98 Cobra. Though bad for his friend, this opened a door of golden opportunity for Jason, who tracked down and bought the remains of the modular Cobra, thus conjuring up the scheme for his cammer-powered commuter. Having a donor car and some ideas, all he needed was some serious help to turn plan into reality.

Despite its low mileage, Jason rightly figured he'd better prep the aluminum DOHC for duty under boost. Though factory endowed with all the crank it needs, the Cobra's reciprocating hardware was deemed too fragile, so it was ditched in favor of Manley rods and Mahle pistons, dished for 8.5:1 compression. Bottom-end rigidity was assured with a Sean Hyland Motorsport girdle and ARP main studs. Though the free-flowing twin-cam heads remain unported, they were secured to the beefed-up block using ARP studs, with Cometic gaskets in between. In the meantime, Jason had Mark Wilkinson at RaceCraft bend up a custom K-member to support the swap.

We assume Jason's close pal Dorian Comeau-a technician at ProCharger's Lenexa, Kansas, headquarters-had a lot to do with the installation of the D-1SC centrifugal, which is pullied for about 15 psi. House of Boost made up a twin intercooler system to keep air-charge temps reasonable at that heady boost level. Twin Bosch fuel pumps, Aeroquip lines, and rails from Wilson Manifolds deliver fuel to 72-lb/hr injectors, while on the air side of the air/fuel relationship, the intake manifold and throttle body remain stock. The mass air, however, was turfed out, as it wasn't needed with the FAST speed-density engine-management system chosen as the easiest way to mate the modular powertrain with the Fox chassis. Jim Summers got the call to do the delicate job of tuning the combination for all the driveability and reliability expected of a daily driver.

At this point, we need also note that the generous donor car didn't just give up its engine; Jason also liberated the Cobra's Hydra-boost brake system, including front and rear discs, along with its rear axle assembly, air conditioning, and lots of miscellaneous hardware to speed the swap process.

After many late nights and long weekends, the resulting successful fusion of two generations of Mustang could be thought of as a bit of a Frankenstein, yet the only thing that might be considered monstrous is its power output. Even so, as this is being written, Jason and his co-conspirator Dorian are busy swapping the D-1SC blower for the even more potent F-1A. Guess that rush-hour commuting traffic must really move along in Jason's part of the world.